The main risk factors for breast cancer can be usefully grouped into four major categories-family history/genetic, reproductive/hormonal, proliferative benign breast pathology, and mammographic density. These factors are briefly reviewed and quantitative estimaters of risk are given. A computer programme for combining them to produce individualized risk profiles is described. The ongoing IBIS-II trial of chemoprevention for high risk postmenopausal women is presented as one approach to managing high risk women.